Overhead projectors for projecting an image of indicia on a transparent film (a transparency) in general include a light source, a stage upon which the transparency is positioned, a projection lens supported above the stage, and a mirror associated with the projection lens. Light from the source is directed through the transparency, to the projection lens and is reflected by the mirror to a vertical surface for viewing by an audience.
Some types of overhead projectors are termed transmissive type projectors since the light source is included in a base enclosure and the light is directed from the base through the transparency and to the projection lens. To make the base as small as possible for transportation, there is typically included a planar mirror in the base to fold the path of the light from the source. To further decrease the size of the base, this base mirror may be pivoted so that the mirror may be rotated into the base. For use, the base is supported by legs and the mirror pivoted through an opening in the base to its operational position.